Mine prop



United States Patent O MINE PROP Konrad Grebe, lbbenburen, Germany Application September 23, 1950, SerialNo. 186,387 Claims priority, application Germany October 1, 1949 21 Claims. (Cl. 248-356) The invention relates to a mine prop and particularly to an hydraulic pressure operated resilient mine prop whlch is provided with a safety or pressure release valve, or discharge valve.

The prop consists of a plurality, and preferably three superposed vertically displaceable sections and elastically expandible means operatively connected with these sections. The adjustable release valve opens, a certain predetermined pressure capacity ofthe prop is exceeded, for the period of the excess load, whereupon a pressure medium, for instance oil, supplied to the prop flows from its pressure space into a reservoir and the prop resumes again its normal length. i

It has been suggested to provide an air buier in the pressure chamber of the mine props above the levelv of the pressure medium, having an air pressure which substantially corresponds to the load carryingcapacity ofthe prop. The air butter is compressed before the maximum carrying capacity of the prop is reached. In replacement of this air buffer helical springs have been applied which are compressed in the initial stage of the loading of the prop. The installation and use of these devices did not provide for a satisfactory operation of the props.

It is the primary object of the invention to prevent premature destruction of theprops upon their exposure to sudden excess loads, for instance, sudden mountain pressures and impacts.

It is a further object of the invention to provide means whereby the safety and pressure release valves commonly used with these props are quickly opened to permit a fast discharge of the pressure medium from the pressure space.

It is also an object of the invention to elastically take up sudden air pressures and to thereby protect the props.

In compliance` with these' objects an elastically expandible buffer member is provided of which the pressure pick-up capacity lies above the predetermined load carryingcapacity of the prop.

Sudden air pressures and impacts are elastically taken up by the buffer and the prop is in this manner protected against premature wear and destruction.

Means are provided to effect a gradual outflow of the pressure medium from the pressure chamber of the prop until the same has resumed its initial position. By means of this mutual or exchange action of the pressure chamber and the buffer a satisfactory pressure carrying capacity of the prop is secured for long operative periods.

Moreover, the prop is automatically returned after sudden load increases in its initial position and is always ready to meet sudden pressure impacts.

Two modications of the invention are illustrated in the attached drawings.

In these drawings,

Fig. 1 is a vertical sectional elevation of one modification,

Fig. 2 is a side view of a second modification of the prop in the compressedposition showing the top and base supporting member, f h

Fig. 3 is a part longitudinal sectional view on lme 3 3 of Fig. 2, the top and base member being` omitted,

Fig. 4 is a vertical sectional view of Fig. 2,

Fig. 5 is a horizontal sectional view on' line 5 5 of Fig. 3.

The mine prop shown in Fig. 1 in a vertical sectional.

view is composed of three hollow sections or members which are mutually displaceable along the vertical longltudinal axis of the prop. The center member 1 has an 2,695,764 Patented Nov. 310, 1954 The upper section or member 3 is a` piston which is guided in the center member 1 and is provided with a` sealing collar 4.

An elastic4 buer 6` is` located in the` lower section 5 of the prop and located between its bottom 7 and bottom 8 of the` middle section.i 1.. The cooperation of. prop sections` 1 and 5` is secured by a threaded ring 9 which` may bear against the outer portionflt) of bottom 8.

The center` member 1 of the prop is provided with `a duct 13 formed in a pipe 11 for the supply of the pressure medium inthe direction of arrow x .and a discharge tube or pipe 12 for the discharge of the same. Two valves 15, 14 are provided in the supply pipe 11`; valve 14v is of the repulsion type. Valve 15 has an outside extension rod 17. By means of a lever 18 coacting with rod 17 thev valve 15 may be openedi. The valve` remains closed by the pressure ofy the pressure medium supplied through duct 13 and is opened in an opposite direction tothe ow direction of the pressure medium. Therefore, an undesired pressure accumulation is prevented in the pressure chamberZ; prop-section 5 is provided with a small` bracket.

19 serving as a support for lever 18.

A` valve 21 is providedl in tube 12 containing the pressure discharge duct 20 which is kept` closed in the outflow direction of the pressure medium indicated by the arrow y. This valve 21 is supported in a bracket 22 secured to` prop part 1; it is provided with anl extension rod 23; the length of this extension rod is` so controlled that upon `compression of buffer 6' the rod 231 will strike the upper rim of prop section 5 and the. valve 21 will be opened accordingly.

The extension rod 23 of valve 21 has` aA collar 24 1ocated short of its end. The collar 24ucoacts with lever 25 which is supported on bracket 26 of section 5. For the purpose of producing apreliminary prop pressure, the

length of rod 23 is so dimensioned that, upon compression` of the. buffer 6, a small space x may be formed between ring 9 and extension 10, prior to the contact of rod` 23 with prop member E. The valve 21 may be replaced by a spring-controlled repulsion valve, which opens automatically as soon as a predetermined pressure is reached.

The buffer 6 consists of a closed body having, for instance, two superposed inwardly open, slotted annular tubes 27which are connected by a cylindrical intermediate member 28. Closed caps 29 are provided. at the upper andthe lower end ofthe buffer. provided in the lower cap 29'; after admission of a pressure medium, such as compressed air, tothe buffer 6 the valve opening 31 will be closed by a stopper or by welding or soldering.

The advantage ofthe above described construction consists therein that the operation of the pressure chamber 2, which is here supported on the buffer, is based on a piston action of its lower portion, that this sealing portion has a discharge valve 21, 23, 24 and that the control member of this valve is operatively coupled with a bridge 8 or a similar member located in the pressure chamber.

The prop is operated, asfollows.

Supply and discharge pipes 11, 12 are connected with the supply and discharge conduits of a pressure medium, such as oil. Valve 15 is lifted by lever 18 and the pressure medium enters into pressure chamber 2. The propV is thereby securely positioned between the top and the bottom strata. Since valve 21 is closed, the butfer is compressed as soon as its predetermined pressure pick-up capacity is reached and a small annular space x is formed by the downward movement of the bridge or bottom 8; Shortly before valve rod 23 contacts the upper face 5a of member 5, valve 15 is closed. Valve 14 prevents the return flow of the oil as soon as the rock pressure commences. If now the buffer 6 is further compressed, valve 21 is opened and the oil flows through ducts 20, 23 into a suitable container until valve 21 by the reexpansion of buffer 6` is closed.`

If sudden pressure impacts occur in the mine which greatly exceed the carrying capacity of, for instance 60 t.

of the prop, buffer 6 elastically takes up these impacts; at the same timevalve 21 i`s opened. The pressure medium,

A repulsion valve 30 isoil and the like, is discharged, and the buffer is again expanded and the normal operation of the prop is restored.

An excess loading of the'prop during the setting action is eliminated, even if valve should stay open for a longer period, because in this case, valve 21 opens during the simultaneous compression of buffer 6 for a certain time until the latter restores the equilibrium position.

In conformity with the modification of the invention shown in Figs. 2-5, one casing 5 surrounding the buffer 6 and the pressure chamber 2 may be provided so that the casing of the pressure chamber is not supported by the buffer and a piston longitudinally displaceable in the pressure chamber casing respresents the member which yieldingly presses against the buffer. By connecting the control member of the discharge valve to the bridgeshaped support 35 of the pressure chamber casing, the discharge valve is positively opened during the downward moment of the piston against the action of the buffer, the valve itself being in a protected location. The center member 1 is threaded into the member 6 by screwing, Fig. 4. A pre-loaded buifer 6, Figs. 3, 4, is located between bottom plate 7 and annular collar 9a, Fig. 4. The upper portion of the buffer is shaped as a piston head or bridge 35 which enters into the lower end portion of pressure chamber 2. The buifer head 35 may also be constructed as an independent part which is separated from buffer 6. The buffer is prevented by pins 36, Fig. 3, from rotation on bottom plate 7.

Buffer 6 is inserted into member 5 prior to the mounting of the bottom plate 7; hereupon-this plate is secured to member or part 5 by welding.

Compressed air is entered through bore 31a, Figure 4, excentrically located in piston head 35. The bore 31BL may be closed by a relief valve 30 at the lower end `by a stopper 37 at the upper end, Figure 5. A sealing ring 38 is located between buffer head 35 and collar 9a. This piston head 35 may also be located inthe lower part of pressure member 1.

` A valve 21 serving as a supply and discharge valve is provided in the longitudinal center axis of piston head 35; this valve has an upper extension 21a, Figure 4, which is suspended upon a bridge 40 located in member 1 and provided with holes 39. The extension 21a is displaceable in bridge 40 in such a manner that the valve 21 may be lifted upon admission of the pressure medium. The movement of extension 21a is limited in the downward direction; therefore and upon compression of buffer 6 that is upon a downward movement of bufer head 35 the valve 21 will be separated from its control member 21a.

`Moreover, a bore horizontal 41 is provided in buffer head 35, Fig. 3, which forms a supply and discharge duct for the pressure medium. An excentrically located shaft 42 issituated in the one half of this bore 41; its excentric end piece 43 is directly located underneath the end 44 of extension 21a. Shaft 42 has a square head 45 for the application of a suitable operating tool. The square head 45 is located within a hole 46 in such a manner that the tool may only be applied or removed if the excentric end piece 43 is turned into its lowest position or if the valve 21 is closed.

The pressure supply line 32 which may be connected to a pump and the discharge line 33 leading to a storage vessel, Fig. 3, are connected with bore 41 of the buffer head 35 by a two-way valve 47. This valve is springloaded in such a manner that the bore 41 is continuously connected With discharge pipe 33 over sealing body 48. The valve 47 may be downwardly pressed by hand lever 49 and the valve body 48 is moved into closing position whereas valve body 50 is simultaneously opened. In this manner the pressure medium may pass from pipe 32 along valve body 50 into bore 41. The valve 21 is opened accordingly against the action of a spring and the pressure medium enters pressure chamber 2 and presses piston 3 against the roof level, Fig. 4. If the supporting capacity of the prop is exceeded, the pressure medium is pressed from chamber 2 through the openings 39 of bridge 40 against head 35 and the latter is downwardly pressed. At the same time Valve 21 is lowered and the pressure medium ows through bore 41 and through two-way valve 47, which has assumed its initial position into the discharge tube 33.

"Ihe initial resistance of the buffer is approximately adjusted in conformity with the desired carrying capacity,

whereby valve 21 is closed by the expanding buffer inthe moment where upon outilow of a part of the pressure medium, the normal carrying capacity has been reached.

If the prop is to be removed the excentric shaft 42 is turned and the valve is opened. During the setting of the prop the excentric shaft 42 must be turned back and the valve 21 closed. Therefore the key to be set onto square head 45 is coupled with the excentric shaft 42 in such a manner that the key can only be removed in the closure position of valve 21. The key may also be secured on the square head 45 by a cam attached to the key head which through a slot reaches into an annular recess of bore 46.

The valve 21 may be externally located with regard to the center of the prop; it is also possible to provide a plurality of valves in the buffer head 35. The prop may be made of steel; however, light metal may be usable.

As described above, the valve 21 is liftable in bridge 35 in an opposite direction to the discharge flow of the pressure medium, forming an entering valve. In this manner only one valve is required for the placement or the removal of the prop; also one valve only is used for the production of an automatic yield in cases of excessive pressure; this valve acts during the positioning of the prop as a relief valve and it is opened in case of excessive pressure by the displaceable valve seat.

The piston-shaped closure body 35 of the pressure chamber may be constructed as a separate element. However, it will be more simple to construct this piston as an upper portion of the butter.

It is, of course, possible to provide a separate Valve for the feed and to solidly locate the control member of the discharge valve in the bridge of the pressure chamber.

The invention may be applied to any type of hydraulic props; props may be used for the purposes of the same where the pressure chamber is located in the lower prop member and the space for the accumulation of the pressure medium connected with the overload valve is located in the upper part of the prop.

It may also be possible to connect the discharge from the overload valve with a collecting duct which, for example, is connected with a collecting container leading to all props. In this last mentioned case it may for the setting of the prop be necessary to feed the pressure space of the prop from a reservoirl by a pump.

It may also be possible to use customary props in combination with shorter props, constructed according to the invention. In this case it might not be necessary to use a prop composed of displaceable parts.

Moreover, the invention is successively usable in connection with gaseous pressure media, which is discharged through a nozzle as soon as a certain excess pressure is reached.

The means for taking up overloads may also consist of a strong spring or of an elastic material, such as an elastic resin which is located in a pressure chamber and which will expand to its normal volume upon pressure release.

It may also be possible to locate the buffer and its operating parts in the upper part of the prop.

This invention has been described with reference to a preferred embodiment and it will be understood that many variations and modifications thereof may be resorted to without departure from the scope of the invention as defined in the following claims.

I claim:

1. In a bulfer mechanism, for use in connection with a mine prop having a series of superimposed sections connected for mutual vertical displacement, a pressure chamber formed in one of said sections and adapted to keep said sections in a desired position relatively to each other in the vertical direction, means for supplying a pressure medium to said pressure chamber and means adapted to diminish the pressure within the pressure chamber under the control of the roof pressure, said mechanism comprising an elastic buffer element being positioned in one of said sections of the said series of superimposed sections, said elastic buffer element having an elastic pressure pickup capacity which is greater than the predetermined maximum load carrying capacity of the prop, but is elastically compressed under an excessive roof pressure, and means connecting said buffer with the said means for diminishing the pressure within the pressure chamber whereby the said last mentioned means are actuated by the compressing movement of said buffer. v

2. In a mine prop, having two vertically superposed sections, said sections being inserted into each other for a mutual vertical displacement, a pressure-formed chamber in one of said vertically displaceable sections provided with means for the supply and means for the discharge of a` pressure medium under the roof pressure, the other sectionV forming a piston and being displaceable in said' pressure chamber, in combination, a third bottom section constituting an elastic butler element having an elastic pressure pick-up capacity which is greater than the predetermined maximum load carrying capacity or" the prop but is elastically compressed under excessive roof pressure, and means connecting said buffer with the said means for the discharge of a pressure medium. t

3. In a mine prop according to` claim 2,` together with, lateral pipeslattached to the pressure chamber for the supply and discharge of a pressure medium to said pressure-chamber and from the same. l

4. In a mine prop according to claim 2, further characterized in that lateral pipes are attached to the pressure chamber for the supply and discharge of a pressure medium to said pressure chamber and from the same, valves disposed in the lateral pipes, said valves being provided with extension rods which outsidedly extend from said pipes and said pressure chamber.

5. In a mine prop according to claim 2, in combination with, lateral pipes attached to the pressure chamber for the supply and discharge of a pressure medium to said pressure chamber and from the same, valves disposed in the lateral pipes, said valves including extension rods which outsidedly extend from said pipes and said pressure chamber, brackets attached to the exterior of said bottom section and located beneath said valve rods, and manually operable means supported by said brackets to lift said valves from their seats and thereby to open said valves. Y

6. In a mine prop according to claim 2, in combination with, lateral pipes attached to the pressure chamber for the supply and discharge of a pressure medium to said pressure chamber and from the same, valves disposed in the lateral pipes, said valves including extension rods extending from said pipes and said pres- E including a bottom plate, and said buffer being con fined between said bottom1 plates.

10. In a mine prop according to claim 8, characterized' inthalt the section which houses the pressure chamber including a bottom plate extending `into the upper part of the bottom section which houses the buffer, a`

p fromy slipping fromlsaid lower section.

sure chamber, brackets attached to the exterior of said bottom section and located beneath said Valve rods, manually operable means supported by said brackets to lift said valves from their seats and thereby open said valves, and a repulsion valve located in the duct for the supply of the pressure medium to the pressure chamber between the manually operable supply valve and the point of entry of said duct into said pressure chamber.

7. In a mine prop according to claim 2, together with, lateral pipes attached to the pressure chamber for the supply and discharge of a pressure medium to said pressure chamber and from the same, valves disposed in the lateral pipes', said Valves including extension rods which extending exteriorly from said pipes and said pressure chamber, brackets attached to said bottom section and located beneath said valve rods, and manually operable means supported by said brackets to lift said valves from their seats and thereby to open said valves, the valve rod of the valve for the discharge of the pressure medium from the pressure chamber being provided with a collar at a point short of the end of the rod, said valve rod having a suicient length to abut against the upper face of the bottom section upon downward movement of an upper section.

8. In a mine prop, having two vertically superposed circular sections, said sections being inserted into each other for a mutual vertical displacement, one of said vertically displaceabley sections housing a circular pressure chamber and including means for the supply, and means for the discharge, of a pressure medium, the other section forming a piston and being displaceable in said pressure chamber, in combination, a third circular bottom section, an elastic buffer in the same having an elastic pressure pick-up capacity which is greater than the predermined maximum load carrying capacity of the prop but is elastically compressed under an excessive roof pressure, and means connecting said buffer with the means for the discharge of a pressure medium.

9. In a mine prop according to claim 8, characterized in that the section which houses the pressure chamber and the bottom section, which houses the buffer, each l1. In a mine prop accordingV to claim 8,. further characterized in that said` means for discharging a pressure medium from the pressure chamber comprising a pipe attached to the pressure chamber and a valve inl the s'aidi pipe, said Valve being operatively connected with said buffer 1n such a manner that said valve is opened by the' compressing movement of said buffer and is kept in an open position during thetime in whichl the said buffer is compressed.'`

12. In a mine prop according to claim 8, further characterized in that said buffer comprising a closed body consisting of a plurality of superposed spaced s1ot ted annular tubes and a vertical cylindrical intermediate member supporting said tubes and connected with the same through said slots, and the buffer being filled with a pressure medium.

13. In a mine prop according to claim 8, further characterized in that said buier comprising two spaced superposed annular tubes, a cylindrical hollow closed center member surrounded by said tubes and connected therewith, each tube having an inner slot opening into said closed center member, the buffer being iilled with a pressure medium.

14. In a mine prop according to claim 8, further characterized in that said buffer member comprising a closed body consisting of a plurality of superpos'ed spaced slotted annular tubes and a vertical cylindrical intermediate member supporting said tubes and connected with the same through said slots, a back pressure valve attached to the bottom of said intermediate member, and means' operable to close said valve and the butler upon introduction of said pressure medium.

15. In a mine prop according to claim 8, further characterized in that said buffer member consisting of a pressure chamber filled with an elastic mass, adapted to assume its original shape upon pressure release.

16. In a mine prop as claimed in claim 8, in combination with a piston head carried by the buffer and forming the bottom closure of the pressure chamber, a combined inlet and outlet valve in said closure head, said Valve including a removable upward extension rod and a bridge in the lower portion of the pressure cham` ber to support said valve rod for an upward lift.

17. In a mine prop according to claim 8, further characterized in that said buffer member consisting of a pressure chamber illed with an elastic mass, adapted to assume its original shape upon pressure release, the bridge consisting of a perforated plate and the valve rod passing through the center of said plate.

18. In a mine prop according to claim 8, further characterized in that said butter member consisting of a pressure chamber iilled with an elastic mass, adapted to assume its original shape upon pressure release, the closure head being the upper portion of the buffer, and a valve for the supply of a pressure medium into the butler excentrically positioned relatively to said pressure release valve in said closure head.

19. In a mine prop according to claim 8, further characterized in that said butter member consisting of a pressure chamber lled with an elastic mass, adapted to assume its original shape upon pressure release, a bore formed in the closure head extending at a right angle relative to the longitudinal prop axis, a combined inlet and outlet Valve located in said bore, and a manually adjustable control member for said inlet and outlet valve having an end accessible for its operation from the outside.

20. In a mine prop according to claim 8, further characterized in that said buffer member consisting of a pressure chamber lled with an elastic mass, adapted to assume its original shape upon pressure release, a bore formed in the closure head extending at a right angle relative to the longitudinal prop axis, a combined inlet and outlet valve disposed in said bore, a manually adjustable shaft provided with an inner excentric mem-` ber for the control of the combined inlet and outlet valve, the end of said shaft being accessible from the outside, said bore forming at the same time the inlet and outlet duct for the pressure medium into the pressure chamber.

21. In a mine prop as claimed in claim 8, in cornbination with, a piston head carried by the buer and forming the bottom closure of the pressure chamber, a combined inlet and outlet valve in said closure head, said valve being provided with a removable upward eX- tension rod and a bridge in the lower portion of the pressure chamber to support said Valve rod for an upward lift, a structure defining duct for the supply and the discharge of a pressure medium and for connecting said valve with said combined valve, a spring controlled two-way valve connected with s'aid ducts and with said duct connecting said valve with the combined inlet and outlet valve, the two-way valve making normally connection with the discharge duct, and manually operable means to close the connection with the discharge duct and to establish the ow of the pressure medium to the pressure chamber.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,458,329 Morgan Apr. 3, 1923 1,779,260 Mobley Oct. 21, 1930 1,828,860 Conklin Oct. 27, 1931 1,877,161 Conklin Sept. 13, 1932 1,981,576 Woolfenden Nov. 20, 1934 2,053,759 Adlam Sept. 8, 1936 2,474,464 Cable June 28, 1949 FOREIGN PATENTS Number Country Date 453,560 Great Britain Sept. 14, 1936 

